The extrusion of molten polymers and copolymers onto a moving substrate web is well known. The coating is usually accomplished by melting the polymer in an extruder, extruding the molten polymer through a slit-die to form a molten film and passing the web substrate, for example, a paper web and the extruded film simultaneously between two pressure rolls and thereby bonding the hot polymer film to the paper. Various polymers have been found to be suitable for such a procedure including polyethylene, copolymers of ethylene and propylene and various ethylene-acrylic acid copolymers. In the case of polypropylene and ethylene-propylene copolymers, although the high-temperature resistance is sufficient for extrusion coating application, the resultant films are not sufficiently rigid for some applications. On the other hand, polystyrene exhibits similar high-temperature resistance properties yet is so brittle that when extruded it tends to crack and exhibits poor adhesion to the substrate. The polymers are normally incompatible for blend purposes.